The objective of the IARC Program on the Evaluation of Carcinogenic Risks to Humans is to identify on the basis of all published epidemiological and experimental data exposures to chemicals, complex mixtures, and physical and biological factors and exposure circumstances which may pose a carcinogenic risk to humans, and to publish these evaluated data in the form of IARC Monographs. The Preamble to the IARC Monographs defines the guiding principles in making evaluations of carcinogenicity on the basis of results from epidemiological studies, long-term carcinogenicity studies in animals and other relevant data (e.g., toxicity, metabolism, genotoxicity and mechanistic studies). Priorities for future monographs topics have been established by ad-hoc Working Groups. Since new topics for evaluation will be chosen in part on the basis of future publication of experimental findings, the program also monitors on-going carcinogenicity testing worldwide through the Directory of Agents Being Tested for Carcinogenicity. A Directory of On-Going Research on Cancer Epidemiology is also produced by the Agency. Each volume of IARC Monographs results from the deliberations of an international Working Group of 15-20 experts in epidemiology, experimental carcinogenesis and related disciplines which meets in Lyon for one week; three meetings are held each year. Monographs are distributed to Governments, Regulatory Agencies and interested scientists; they are available via the WHO Distribution and Sales Service. The summarized and evaluated data can be used as an element on which priorities for preventive measures will be decided. The Monographs and related databases will also be available on an IARCancer CD-ROM. The Directory is produced every two years based upon the replies received to survey questionnaires. They are distributed to all collaborating laboratories and governments with the aim of reducing duplication of effort and improving communication between scientists in the area of carcinogenicity testing in animals. The International Agency for Research on Cancer has adequate facilities for meetings and the production of monographs. Scientific staff includes scientists from many different countries who can assist in the evaluation of international scientific literature and provide scientific guidance for the Working Groups.